Conventional apparatuses used to treat substrates with ions include beamline ion implanters and plasma immersion ion implantation tools. Both are appropriate for implanting ions over a range of energies. In beamline ion implanters, ions are extracted from a source, mass analyzed, and then transported to the substrate surface. In a plasma immersion ion implantation apparatus, a substrate is located in the same chamber and the plasma is generated adjacent to the plasma. The substrate is set at negative potential with respect to the plasma and ions that cross the plasma sheath in front of the substrate impinge on the substrate at perpendicular incidence angle. Recently a new processing apparatus that allows control of the extracted ion angular distribution (IAD) has been developed. In this apparatus ions are extracted from a plasma chamber but unlike the beamline where the substrate is located remotely from the ion source, the substrate is located proximate the plasma chamber. Ions are extracted through an aperture of special geometry located in an extraction plate that is placed proximate a plasma. Changing the geometry of the aperture allows changing of the ion angular distribution, i.e., the mean angle and angular spread of the ion distribution. This may be appropriate to treat substrates with 3D structures i.e., that present surface features whose sidewalls are to be exposed to ions, for the purposes of implantation, deposition, etching, or other processing. In order to treat such sidewalls, ions are extracted through the aperture of a certain shape and size to generate an ion beam width and ion angular distribution. Usually the aperture has an elongated shape so that ribbon ion beams having heights of 3-30 mm and widths of 350-400 mm might be extracted. In the case the ion beam is wider than the substrate to be processed (a 300 mm Si wafer for instance) a processing step can be achieved at once by passing the substrate in front of the ribbon beam. If more processing is desirable then the substrate is passed back and forth in the front of the beam as many times as is needed.
On the other hand, in addition to the beam shape and beam current, in a plasma processing system it may be desirable to provide further control over ion angular distribution (IAD). It is with respect to these and other considerations that the present improvements have been needed.